Commonly, reflow soldering is employed for surface-mounting a metallized film capacitor having two metal terminations to a circuit board. In reflow soldering, a paste solder is applied to the metal terminations of the metallized film capacitor, which is positioned suitably on the circuit board. When the circuit board, the capacitor, and the solder paste are heated, the solder paste fuses and forms a liquid solder, which then is cooled, hardens, and connects the metal terminations mechanically and electrically to the circuit board.
As exemplified in Rayburn U.S. Pat. No. 4,580,190 and in Rayburn U.S. Pat. No. 4,531,268, it is known to make a metallized film capacitor from a laminated structure having multiple layers of metallized, dielectric film and having a sprayed, metal termination at each of two ends. When reflow soldering is employed, it is necessary to employ a solderable metal at the exposed surfaces of the metal terminations.
In Langlois U.S. Pat. No. 4,741,077, which discloses a process of related interest for manufacturing metallized film capacitors, burnishing is employed to render deposited metal films more solderable. In Hirama U.S. Pat. No. 4,959,652, which also discloses a process of related interest for manufacturing metallized film capacitors, sandpaper or emery paper is employed for removing a coating resin so as to expose an electrode surface and for roughening the exposed surface before soldering. The Hirama patent also discloses that grooves are formed in the exposed surface, through the coating resin, to improve soldering.
Typically, when metallized film capacitors are burnished, burnishing is practiced in a rotary or tumbling chamber containing abrasive burnishing media. By thus practiced, burnishing tends to round the capacitor ends, particularly near their top and bottom edges. The rounded ends tend to impair reflow soldering. Burnishing with abrasive burnishing media does little to reduce surface porosity, which is detrimental because moisture readily penetrates the porous surfaces. Furthermore, when metallized film capacitors are burnished with abrasive burnishing media, it can be quite difficult to maintain tight dimensional tolerances. Additionally when burnishing thus is practiced, there is some risk of physical damage to metallized film capacitors being burnished.